1. Field of the Invention
This invention relates to a simulated moving bed separation system, more particularly a simulated moving bed separation system equipped with packed bed-washing means for washing the packed beds of the simulated moving bed separation system. Specifically, the simulated moving bed separation system of this invention can be washed for a shorter period of time than prior art simulated moving bed separation systems.
2. Prior Art
Known simulated moving bed separation systems comprise a flow path constituted by packed beds, each of which contains a separation filler packed therein, connected in series and endlessly via a piping to each other, a desorbing liquid introducing port for introducing the desorbing liquid into the flow path, an extract draw-out port for drawing out the extract rich in strongly adsorptive constituents of a feedstock from the flow path, a feedstock introducing port for introducing the feedstock containing constituents to be separated into the flow path, and a raffinate draw-out port for drawing out the raffinate rich in weakly adsorptive constituents of the feedstock from the flow path. The flow path is provided with a pump for forcibly circulating the liquids through the flow path. Further, the desorbing liquid introducing port, the extract draw-out port, the feedstock introducing port and the raffinate draw-out port are arranged in this order in the direction of flow of a liquid circulated through the flow path (hereunder referred to as xe2x80x9ccirculation liquidxe2x80x9d), and designed to be intermittently shifted in the direction of flow while being kept in this order.
These simulated moving bed separation systems are featured in that these systems can continuously work, save an amount of the desorbing liquid used to a larger extent than batch-type chromatographic separation systems, and obtain an extract containing a high content of objectives. Thus, these systems have heretofore been used for separation or purification of drugs, pharmaceuticals, agrochemicals, perfumes, sucrose, etc.
These systems are in general cleaned by allowing a washing liquid such as a desorbing liquid to pass through the flow path when they are to be stopped working.
However, since the flow path for the circulation liquid comprises packed beds connected in series as mentioned, the pressure loss of the flow path is a total of all the pressure losses in the packed beds and piping. Accordingly, the total pressure loss of the flow path through which the circulation liquid is allowed to pass is very large. Thus, it is very difficult to allow the washing liquid to flow at a high speed through the flow path. Furthermore, since the washing liquid introduced into the flow path is allowed to pass all the packed beds and piping and thereafter discharged, it takes a very long period of time until the washing liquid is discharged after it is introduced. Thus, a very long period of time is required for washing of the flow path. These systems have such a further problem that impurities retained in one packed bed entrain on the circulated washing liquid to transfer to another packed bed, which is stained by the impurities.
One object of this invention is to provide a simulated moving bed separation system from which the above-mentioned problems of the prior art systems were eliminated.
Another object of this invention is to provide a simulated moving bed separation system, the flow path of which can be washed for a shorter period of time, and one packed bed of which is not stained by impurities retained in another packed bed.
The simulated moving bed separation system of this invention is as follows:
(1) a simulated moving bed separation system, which comprises a packed bed assembly consisting of a plurality of packed beds, each of which contains a filler packed therein, connected in series and endlessly to each other, and constituting part of a flow path through which liquid is forcibly circulated, provided with a desorbing liquid introducing port for introducing the desorbing liquid into the flow path, an extract draw-out port for drawing out an extract rich in strongly adsorptive constituents of a feedstock to be separated from the flow path, a feedstock introducing port for introducing the feedstock into the flow path, and a raffinate draw-out port for drawing out a raffinate rich in weakly adsorptive constituents of the feedstock from the flow path, wherein said desorbing liquid introducing port, said extract draw-out port, said feedstock introducing port and said raffinate draw-out port are arranged in this order in the direction of liquid circulation through the flow path, and designed to be intermittently shifted along the flow path while being kept in this order, and further provided with a packed bed-washing means for washing the packed beds by supplying a washing liquid into the packed beds at one end thereof, respectively; and
(2) A simulated moving bed separation system according to (1) above, wherein said packed bed-washing means washes one unit consisting of one or two of the packed beds at one time, and switches from one to another unit at a predetermined interval to repeat the washing of the units of packed beds.